Dengue virus (DENV) is the most clinically important arbovirus and a Category A bioterrorism agent. As with other positive stranded RNA viruses, DENV rearranges cellular membranes to establish unique cytosolic structures that are the sites of replication complex formation. We found that DENV co-opts cellular fatty acid biosynthesis to establish its sites of replication. The viral NS3 protein binds to fatty acid synthase (FASN), recruits it to sites of viral replication, and stimulates its activity. The NS3 domain required for FASN binding has been defined. Mutation of the FASN interaction domains established that the NS3-FASN interaction is absolutely essential for replication. Importantly, FASN inhibitors block the replication of DENV and other flaviviruses including West Nile virus and yellow fever virus. Additionally the FASN pathway has been implicated in the replication of many other viruses, including HIV, HCV, influenza, and HCMV. This suggests that FASN inhibitors may be a broad spectrum antiviral therapeutic if tolerated. We have identified a FASN inhibitor lead compound, IPI- 9119, that fits this criteria. It inhibits FASN in cell culture and in the liver and lungs of ice. The compound is orally bioavailable and irreversibly inhibits the thioesterase domain of FASN. Toxicity studies in vitro and in mice demonstrate that the inhibitor is well tolerated with minimal toxicity issues. This project is a collaboration between three groups. The Randall lab has characterized the DENV- FASN interaction and has assessed antiviral activity of FASN inhibitors in vitro. The Diamond lab are leaders in flavivirus research and are highly experienced with DENV and West Nile Virus animal models and inhibitor testing. The Infinity group developed the FASN inhibitor class and characterized its efficacy and (lack of) toxicity in vivo. They have expertise in medicinal chemistry, animal toxicity testing, and analysis of IND-enabling studies. We propose to test the efficacy of this compound against DENV and WNV infection in vitro and in mouse models and then build toward an IND filing. We will validate the efficacy of FASN inhibitors against DENV infection in vitro and in vivo. Anti-DENV activity will be characterized in cell culture and mouse models, while mechanisms of resistance are evaluated. Further drug evaluation assessing pharmacokinetics, pharmacodynamics, and various toxicity assays will be performed to advance these compounds toward IND filing. This project will move a likely broad-spectrum antiviral that targets a well-characterized virus-host interaction in dengue virus replication inhibitor into IND filing for clinical trials. Importantly, although the inhibitor targets an important cellular enzyme, it is non-toxic in mice.